DE2848309A1 - LAMINATED PLATE PART, IN PARTICULAR AIRCRAFT CONTROL SYSTEM PART AND AIRCRAFT CONTROL SYSTEM EQUIPPED WITH IT - Google Patents

Description

UNITED TECHNOLOGIES CORPORATION Hartford, Connecticut 06101, V.St.A.

Laminated plate part, in particular an aircraft control system part, and an aircraft control system equipped therewith

The invention relates to a laminated plate part, in particular an aircraft control system part, and a device equipped therewith Aircraft control system in which the control surface or the control part receives an input variable from a pilot or by automatic control over a series of interconnected and relatively movable parts, such as Angle levers, rollers, rods, etc., receives, and in particular relates to a part of such a system, which is constructed in such a way that it is less endangered by projectiles, so that the system and its control function can still be operated can continue to exercise after a projectile has passed through the part.

So far, many efforts have been directed towards improving the armouring of aircraft, ships, etc. but with the idea on which the reinforcement is based

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consists of building a part in such a way that it offers resistance to a projectile passing through it and the projectile as much as possible ricochets. Known reinforcement structures of this type are shown in the US-PSs 3 179 553, 3 604 374 and 3 962 976. The disadvantage is that the reinforcement, which is made in such a way that it ricochets off a projectile of a special caliber, is ineffective becomes when larger caliber projectiles are aimed at them, and ultimately, especially in the field In aircraft engineering, armor cannot be reinforced by increasing its volume beyond a practical limit is increased because the aircraft must be able to take off from the ground and to the extent necessary personnel and / or to take freight with you.

Angle levers and other aircraft control parts have been made from aluminum alloy castings and / or steel or aluminum forgings manufactured that are prone to breakage when shot at with handguns, creating redundancy Systems and / or armor plates are required, which is considerable additional cost and considerable bring additional weight. The invention differs from the known reinforcement in that the aim is not to make parts in such a way that projectiles ricochet off, but in such a way that the part is projectile hit can survive and remain operable to perform its intended function after a projectile has passed through it is.

The invention provides an aircraft control system part which can continue to function after a projectile hit it and went through it.

According to the invention, the aircraft control system part is made up of one another connected layers, with the outer

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or floor exit layer of a selected thickness and Has tensile strength, so that the petal-like ridges that are in it through an impacting and passing through Projectile generated will be deformed when the burrs are under the control pressure with associated parts come into contact following the damage in order to avoid the secondary jamming of the control system and to allow continued operation of the control system with the ridges so deformed.

According to a further feature of the invention, the part is preferably made up of side plate parts made of three-layer laminates manufactured, whereby the middle layer is twice as thick as the end layers and the layers by an elastomer-modified Epoxy are bonded together to thereby improve the strength of the part and the actuation of the part following a projectile damage, so that the best compromise between survivability and redundancy is achieved.

The invention also provides a part with less risk by projectiles and with better survivability without increasing the volume or weight of the same and at a lower cost through the use of layered sheets instead of fully machined forgings made of the same alloy.

The invention also provides a part with a lower risk of projectiles by using glued together Layers for strengthening the part by taking advantage of the high surface stress fracture toughness of surface material, which is a multiple of the value of the lower surface elongation of heavy forgings.

The invention also provides a part in which the three-ply Laminate construction with elastomer modified epoxy

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resin compound are less endangered by bullet damage can / because it has a higher bullet resistance, less lateral damage and a higher bullet impact reflection at the interfaces between the layers and the adhesive.

According to the invention, the aircraft control part is made of layers which are glued together so that there is a has greater strength than a monolithic structure and is therefore able to withstand greater projectile damage to cope with failure without failure, and burrs are formed on its projectile outlet plate, which are under the control pressure are deformable by mutual influence with interacting parts following the projectile damage and therefore allow further operation of the system.

The lower risk from projectiles and the higher survivability are achieved according to the invention without loss of performance and at lower costs.

According to the invention, one or more parts of a master flight system are made up of interconnected layers rather than monolithically manufactured so that projectile damage effects are reduced in a ratio of 5: 1 and thereby the ability of the part to survive by avoiding secondary lockup conditions due to burrs is enlarged in the projectile exit layer so that the system remains operable and not by a single projectile hit one of its parts is rendered inoperable.

Several exemplary embodiments of the invention are described in more detail below with reference to the accompanying drawings.

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wrote. Show it:

Fig. 1 is a monolithic plate part for

Illustration of the bullet damage caused by an impacting and projectile passing through is caused,

Fig. 2 is a plate part with three together ver

Glued layers of the same thickness to illustrate the damage to the bullet, the caused by a projectile impacting and passing through,

FIGS. 3 and 3a are a drawing and a photographic, respectively

the projectile damage to such a monolithic plate part and to such laminated plate part, which is made of the same metal and with the same total thickness are made, the bullet damage being exactly by the same bullet hit is caused

Fig. 4 shows a preferred embodiment of a

laminated plate part according to the invention to illustrate that the middle the three layers is twice as thick as the end layers,

Fig. 5 is a plan view of a laminated plate part

of the type shown in Fig. 4, which has been hit by a projectile which has passed through and has made its "impression", the lateral damage in the layers and the damage-reducing effects of the being used to glue the layers together

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elastomer-modified epoxy resin can be recognized,

Fig. 6 is a stress-strain curve for a

metallic laminate and the elastomer-modified epoxy resin adhesive layer, to show that the metallic laminate fails first and that the adhesive does not fail until one is substantial major elongation or deformation of the order of 6: 1 or 8: 1 occurs,

Fig. 7 is a diagram in which the fracture toughness

speed is plotted against the sheet thickness to illustrate that a monolithic Part of selected thickness has a significantly lower fracture toughness than a laminate part whose thickness is approximately is equal to one third of this thickness,

Figure 8 is a graph of lateral damage

in a laminate panel part of the type shown in Fig. and a monolithic one Plate part of comparable thickness and made of the same material when hit by a 12.7 mm bullet at an angle under 45 ° and at different projectile velocities,

Fig. 9 an angle lever, which according to the invention

is part of an aircraft control system and is relatively movable with others Sharing the same interacts when connecting the controlling mechanism with the controlled mechanism,

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FIG. 10 is a section on line 10-10 of FIG

Fig. 9,

11 is a section on line 11-11 of FIG

Fig. 9, and

FIG. 12 is a partial view of the angle lever from FIG

Fig. 9 showing the individual application of sacrificial tapes to the side panel members shows.

For a better understanding of the invention, the research results will first be explained, which in an investigation the projectile hazard of aircraft parts have been achieved, and then it is explained how these research results has been applied in a practical embodiment are.

It is common in practice to have a remote surface or part to be controlled, such as a helicopter tail rotor or aileron, with the pilot's stick or with an automatic Control via a series of interconnected angle levers, rollers and connecting rods to connect so that the reference variable entered by the pilot or the automatic control is passed on via the connection system and the controlled part is reliably controlled. If a projectile damage results in the failure of the connection system or the Blocking of the same causes the control function can no longer be exercised. It was therefore the aim of the investigation study bullet damage and research results exploit to achieve that the parts of the system are less endangered by projectiles.

Since a bell crank is an easy-to-understand mechanism and a typical part in such a control system,

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2848303

be the investigation and exploitation of the research results described with reference to a bell crank, but it should be noted / that any such Control part can be produced using the teaching of the invention.

Angle levers have been manufactured so far that they have sufficient strength to withstand the control force that it is exerted on it by the pilot, and this control force on the controlled part via the connection system transferred to. Conventionally, toggle levers are made of solid metal of selected strength, such as forged or cast aluminum, made to withstand this control force.

Shot tests on such one-piece angle levers with a massive construction, so-called monolithic construction, showed that the type of failure when the projectile hits and through going through this monolithic construction is a massive perturbation, i.e. a shear punching of a volume of metal with about the diameter of the projectile, which is followed by a wedge effect of the projectile, which results in the impulse voltages adds in the structure and tears as well as delaminations away from the hole or "indentation" which the projectile makes, leads. The result is the formation of a metallic crack along the central part of the monolithic Construction 10, for example at location 12 in Figure 1, and substantial damage and removal of metal both on the storey entry side, for example at point 14, and on the storey exit side, for example at the point This severe projectile damage to the monolithic structure leads to severe weakening of the part and causes in all likelihood the failure of a part, such as a monolithic bell crank.

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The investigation included bullet tests on laminated structures such as the three-layer or laminate structure 18 of Fig. 2, which has three layers of equal thickness and the same overall thickness as the monolithic structure of Fig. 1 has. In the construction of FIG. 2, an "impression" 20 of the bullet in the first end layer 22 and also made in the middle layer 24 and in the other, outer, end or projectile outlet layer 26. A certain one However, the amount of cracking occurs in the second layer 24 and an even greater amount of cracking occurs in the third Layer 26 on when the bullet passes through and a dislocation or folding of the laminate metal that acts as a flash in the direction in which the projectile moves. This investigation shows that the Total floor damage in the laminate construction of Fig. 2 is about a quarter of the projectile damage that is caused in the monolithic construction of Fig. 1 is caused.

The drawing of FIG. 3 and the photograph of FIG. 3a show, on the left, the projectile damage that occurred on the monolithic Construction of Fig. 1 occurs and a centerline shear failure, Includes tearing and chipping on the rear surface, and on the right the chipping effect and total bullet damage on a laminar construction of Figure 4 which is the same overall thickness as the monolithic construction of Fig. 1 and has been penetrated by a projectile of the same caliber as the monolithic construction is.

All shot tests carried out during the investigation and described here were carried out with a ratio of total material

thickness to projectile diameter of 1: 3 carried out, which is known to cause the maximum projectile damage.

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In the preferred laminate construction 28 of the invention shown in FIG. 4 and having the same strength as the construction of FIG. 2, again three layers are used which together are the same thickness as the monolithic construction of FIG. 1 and the laminate construction 18 of Fig. 2 with layers of equal thickness, but in the construction of Fig. 5 the middle layer is twice as thick as the end layers 34 and 30. In the construction of Fig. 5, the outer, end or projectile exit layer 34 is through which leaves the laminate plate 28 through the projectile, made of a material whose thickness and tensile strength are selected so that the burrs formed in the layer 34 by the projectile striking and passing through are deformable or displaceable by the control force acting on them is exercised by those parts with which the aircraft control part, which contains the laminar plate 28, cooperates, namely after bullet damage, which enables further actuation of the control. Due to this deformability of the projectile exit layer-Ausgratungen the part has a better tolerance projectile, d _t h. is less endangered by projectiles, so that it can survive projectile damage and remain operable.

In the laminar construction shown in Fig. 4, it is important that the layers 30-34 be elastomer-modified Epoxy resin are bonded together in such a way that the adhesive has the maximum degree of elasticity in the event of failure (e) is given, which is preferably 30-60%. The importance of such a binder or adhesive in improving the strength of laminar panels 28 or 18 is best understood with reference to Fig. 5, which in plan view the laminar plate 28 of FIG. 4 as well as the projectile "impression" 20 and the laminate crack and burr damage shows that of projectile impact and passing through of the projectile is caused by the layers.

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Such a crack in the projectile exit layer 34 is shown at the point 36, while at the point 38 the non-failed adhesive between the layers 34 and 32 around the leading edge of tear 36 is shown. Since the adhesive 38 has not failed, the crack 36 do not propagate beyond him. Likewise, cracks 40 in layer 32 meet non-failed areas 42 of the adhesive between layers 30 and 32 which prevent the cracks from propagating beyond them. This elastomer modification of the epoxy resin results in a more pliable adhesive and consequently less adhesive damage and less delamination after a bullet has passed through.

6 shows a stress-strain diagram for such a metal layer, for example layer 34, as curve A, its failure occurs at a point B (elasticity (e) at failure approximately 8%), and for the adhesive layer as Curve C, the failure of which occurs at point D and the elasticity of which at failure (e) is about 50%.

It can thus be seen that the laminar panel member 28 is reinforced by the use of this type of adhesive because this shear strength of the adhesive must be overcome before the crack can propagate further. It can be seen from FIG. 6 that the layer represented by curve A, which can be the projectile exit layer 34, fails at point B, but that the adhesive to which it is bonded only becomes significant at one point greater stress - on the order of 3: 1 or 8: 1 greater - fails at point D, which is why the crack in the layer can only propagate further when the adhesive has failed in this greater state of stress.

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An elastomer-modified epoxy resin with the desired properties is available from Narmco Materials, Inc., Costa Mesa, California, V.St.A., under the designation M-1113, expelled.

Shot tests on laminated panels showed that the damage increased in successive layers, and the three-layer board was chosen as the best compromise between survivability and redundancy.

The second reason why laminar construction is a has greater strength over the monolithic construction, can be seen from a consideration of FIG. 7, which in FIG a diagram showing the fracture toughness (K) plotted against the sheet metal thickness (of a sheet metal part through which a projectile passes through) is applied. The curve shows that the fracture toughness of the monolithic part 10 is substantially is half that of a layer, such as layer 26, the thickness of which is equal to one third of the thickness of the monolithic part 10, and that of course the fracture thickness of the even thinner end layer 34 of FIG is even bigger.

It can accordingly be seen that the laminar panel construction of the monolithic construction both because of the larger The fracture toughness of the thinner layers as well as the strength-increasing property of the special adhesive is superior. The laminar panel construction is further superior because if is the preferred embodiment of Fig. 4 is used, the thin projectile outlet layer has burrs, which at control pressure by mutual Influencing with interacting parts in connection with a projectile damage are easily deformable, whereby a secondary blocking of parts is avoided and the rest

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Actuation of the parts produced in this way is made possible.

Fig. 8 shows the improved performance from the point of view of side damage, i.e. total damage of the bullet hole, cracks and cracks of the preferred laminar panel construction of FIG. 4 with reference to FIG Curve 44 with zero scattering area 24 compared to a monolithic construction of the same thickness, both of them obliquely at an angle of 45 ° with a 12.7 mm bullet were shot at, with the upper, the typical and the lower limit of damage to the monolithic structure are represented by curves 46, 48 and 50, respectively. The material for both the monolithic construction and the Laminate construction was aluminum 7075-T6. 7075-T6 is a standard designation from the aluminum industry. A similar one The laminar construction had an advantage over the monolithic construction when using a 7.62 mm bullet achieved. The test results showed that the side damage decreased by ratios of 3: 1 and 4: 1 in the laminate construction compared to the monolithic construction was reduced when the bombardment with projectiles with a Calibers of 7.62 mm and 12.7 mm respectively.

Figure 9 shows a bell crank made using the preferred construction of the invention has been to make it less dangerous by projectiles. The deflection 52 is on a conventional holder of the aircraft is mounted so that it is rotatable about a pivot point 56. An input rod 58 either through the Pilot or by an autopilot can be operated, is hinged to the deflection 52 rotatably about an axis 60, while an output rod 62 at the deflection 52 by one Axis of rotation 64 is rotatably articulated. In this way, the action of the control stick 66 of the pilot or one another suitable mechanism is transmitted to the diverter 52 through the input rod 58 to either the diverter

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to rotate clockwise or counterclockwise about the axis of rotation 56 and an equal movement of a controlled element 68 to give over the output rod 62. The controlled element 68 may be an aircraft part controlled by the pilot / such as an aileron or a helicopter tail rotor. In all likelihood there will be several more Deflections, connecting rods / rollers, etc., in the connecting chain 67 between the input control part 66 and the controlled part 68 may be present, but the structure of FIG. 9 has been chosen for simplification purposes.

According to FIGS. 10 and 11, the deflection or the angle lever 52 side plate parts 70 and 72 which have the same structure. The side plate members 70 and 72 are each made a middle layer 76 and end layers 78 and 80 formed with the elastomer-modified epoxy resin described above and are glued to the middle layer 76, the latter being twice as thick as the end layers 78 and 80. The side panel parts 70 and 72 are glued to and selectively spaced apart by a spacer 82 separated. The spacer 82 is preferably made of viaben material and preferably either with foam filled or with high-strength fiberglass material, which is impregnated with epoxy resin and hardened, encased in order to make the spacer 82 waterproof.

The investigations have shown that the three-layer structure for the formation of the end plates 70 and 72 is optimal, both because of the increasing burr in the order of the penetrated layers and because of the additional The weight of the additional layers of adhesive that add to the total weight of the part. The three-shift The structure provides sufficient redundancy (security) and at the same time limits the damage due to the transmission surge.

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In the preferred construction of the invention, spacer 82 is made from 36.9 kg / m ³ aluminum honeycomb material (although Nomex ^ could have been used, and layers 76-80 are made from 7075-T6 aluminum, the End layers 78 and 80 have a thickness of 1.02 mm, while the middle layer 76 has a thickness of 2.1 mm. This material is known to have a tensile strength of 4412.8 bar. when the end layer of 7075-T6 aluminum was 1.02 mm thick. The control force available to deform the flashes was 4315 N. The control force "available to deform the flashes in a typical helicopter control system is about 4448 N. Since the force required to deform thin sheet metal is equal to the reciprocal of the square root of the thickness of the material, ie F «1 /" / "t \ where F, _ _Y is the yield point and t g Depending on the material thickness, other suitable materials can be selected for the layers 76-80 or just the bullet exit layer 80, since the material yield strength will be known and the layers with a suitable thickness to fulfill this function of deformable flashing can be produced by applying the following equation:

^F TY I 1

^f tyI ²

where F _rrv | 1 is the yield strength of aluminum 7075-T6, ie 4412.8 bar, where t .. is the thickness of the tested projectile exit layer 80 made of aluminum 7075-T6, ie 1.02 mm, where Ρ _τγ | ^{2 is} the known yield strength of the new layer material and where t _? is the thickness of the new bullet exit layer material. The tests did not go beyond evidence of an acceptable degree of deburring for a 1.02 mm thick bullet exit layer 80 of 7075-T6 aluminum in the construction of Figures 9-11 , in which all

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Layers of aluminum were 7075-T6 and the adhesive was M-1113, so those skilled in the art would recognize that a thicker one Bullet exit layer made of aluminum 7075-T6 may also be acceptable, as can a 1.02 mm thick bullet exit layer could be made of a second material with lower yield strength. The investigations led to deform the excavated bullet exit layer, but if a more brittle material such as beryllium were used, the burrs would likely be sheared off. Both the deformation of the ridges as shearing them are also acceptable for continued system operation. The laminates could be made from Ti-6A1-4V (Titanium, 6 aluminum, 4 vanadium) or Ti-15V-3Al-3Cr-3Sn-titanium or similar titanium sheet alloy, steel, magnesium or a composite fiber construction depending on the requirements of the plant concerned. In the preferred embodiment, the thickness of the spacers was 82 chosen so that the plate parts 70 and 72 had a distance of 25.4 mm, and there were cans used, which were chosen so that the axes of rotation 60 and a mutual distance of 102 mm and the axes of rotation 60 and 64 were at a distance of 76.2 mm from the axis of rotation 56, as is shown in FIG.

According to FIG. 9, sacrificial or predetermined breaking bands 84 and 86 are completely wrapped around the eyes of the angle lever 52. These Sacrificial tapes are made of unidirectional, epoxy resin-soaked fiberglass threads, which in the manner shown wrapped around the exterior of bell crank 52 and then cured to bond them to it. the specific property, i.e. the tensile strength of the fiberglass thread material and the number of wraps of the angle lever 52 with the thread material are chosen so that the failure load of the sacrificial strips 84 and 86 is equal to the Is the force exerted on the laminate panel members 70 and 72 by the assumed projectile. In the process of the

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Holding the layers together, these sacrificial tapes serve to dampen initial floor loading, with the layers remaining in their original position and only then exerting a peel load on the layers when the sacrificial tapes fail. That is because the strength of the sacrificial ligaments fails. This is because the strength of the sacrificial tapes is chosen so that it is equal to the load exerted on the laminate plate parts 70 and 72 by the projectile. The bands 84 and 86 are indeed shown 9 is wound around the entire deflection in the structure of Fig., Shown in FIG. 12 could instead but also individual victim ribbons are used 88 and 90, which are wound at appropriate locations around the individual plate parts and 72.

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Claims (23)

Patent claims: Laminated plate part, characterized by: a) a first side plate part, b) a second side plate part, c) a spacer which is arranged between and connected to the side plate parts and keeps the side plate parts at a selected mutual distance, d) each side panel portion having three interconnected layers, of which the middle layer twice as thick as the other layers and where the outer layer is a selected thickness and Has tensile strength so that those formed therein by a projectile striking and passing through Burrs due to mutual influence with assigned parts after such a bullet damage are sufficiently deformable to the bullet damage tolerance improve the part and allow its continued operation, and e) at least one sacrificial tape which envelops the plate part and is glued to the same and a thread part with it has a high modulus and selected tensile strength, which is wound with a certain number of turns around the plate part, so that the failure of the sacrificial tape causing load is equal to the force to be expected which will be exerted on the plate parts by the projectile impact and passage is exercised. 2. Aircraft control system part that is used with associated parts when performing a control function on an aircraft interacts and is movable relative to these parts, characterized by: a) a first side plate part, b) a second side plate part, c) a spacer which is arranged between and connected to the side plate parts and holds the side plate parts at a selected mutual distance, and d) each side panel portion having three interconnected layers, of which the middle layer twice as thick as the other layers and where the outer layer is a selected thickness and Has tensile strength so that those formed therein by a projectile striking and passing through Burrs due to mutual influence with assigned parts after such a bullet damage are sufficiently malleable to improve the part's bullet damage tolerance and its continued To allow actuation. 3. Part according to claim 2, characterized in that the layers are joined by an elastomer-modified epoxy resin are connected. 4. Part according to claim 2 or 3, characterized in that the spacer is made of aluminum honeycomb material. 909825/0633 5. Part according to claim 4, characterized in that the layers are made of 7075-T6 aluminum. 6. Part according to claim 4, characterized in that the layers of Ti-6-Al-4V-titanium - or Ti-ISV-SAl-SCr-SSn-titanium or similar titanium sheet alloy are made. 7. Part according to claim 5, characterized by a device to waterproof the spacer. 8. Part according to claim 3, characterized in that the elastomer-modified epoxy resin has an elasticity at failure of 50%. 9. Part according to one of claims 2 to 8, characterized by at least one sacrificial tape which envelops the part and is glued to the same and has a thread part with high modulus and selected tensile strength, which with a certain Number of turns is wound around the part, so that the same load causing the failure of the sacrificial tape is the expected force that will be exerted on the side plate parts by the projectile impact and passage. 10. Part according to claim 9, characterized in that a such sacrificial tape is wrapped around each side panel portion in at least one location. 11. Part according to claim 4, characterized in that the Honeycomb material is 36.9 kg / m aluminum honeycomb material and has a height of 25.4 mm and that the layers are made of 7075-T6 aluminum consist, which has a tensile strength of about 4412.8 bar, with the middle layer 2.06 mm thick, while the other Layers are 1.02 mm thick. 909825 / Q633 12. Part according to one of claims 2 to 11, characterized in that that it is an angle lever or deflection part. 13. aircraft control system, with a control input device actuated by the pilot, with a controlled one remote from the input device Facility, with a device which connects the input device to the control device, so that the input device is effectively connected to the controlled device in order to control the same, wherein a plurality of interconnected and cooperating parts are provided which are used to fulfill the control function interact with associated parts and are movable relative to the same, characterized in that at least one part is provided is which contains: a) a first side plate part, b) a second side plate part, c) a spacer between the side plate parts arranged and connected to these and the side plate parts in selected mutual Keeps your distance, and d) each side panel portion having three interconnected layers, of which the middle layer twice as thick as the other layers and where the outer layer is a selected thickness and Has tensile strength so that those formed therein by a projectile striking and passing through Burrs due to mutual influence with assigned parts after such a bullet damage are sufficiently malleable to improve the part's bullet damage tolerance and its continued To allow actuation. 909825/0633 14. System according to claim 13, characterized in that the layers through an elastomer-modified epoxy resin are connected to each other. 15. System according to claim 13 or 14, characterized in that that the spacer is made of aluminum honeycomb material. 16. System according to claim 14 or 15, characterized in that that the layers are made of 7075-T6 aluminum. 17. System according to claim 14 or 15, characterized in that that the layers are made of Ti- 6Al -4V-titanium. 18. System according to claim 16 or 17, characterized by means for waterproofing the spacer. 19. System according to one of claims 13 to 18, characterized in that that the elastomer-modified epoxy resin has an elasticity at failure (e) of 50%. 20. System according to one of claims 13 to 19, characterized by at least one sacrificial tape, which envelops the part and is glued to it, and a thread part with a high modulus and selected tensile strength wound around the part with a certain number of turns so that the Sacrificial tape failure load is equal to the force to be expected, which is caused by the projectile impact and passage on the Side plate parts is exercised. 21. System according to claim 20, characterized in that such sacrificial tape is wrapped around each side panel portion in at least one location. 22. System according to claim 15, characterized in that the aluminum honeycomb material is 36.9 kg / m ³ aluminum honeycomb material with a height of 25.4 mm and that the layers are made of 909825/0633 7075-T6 aluminum, which has a tensile strength of about 4412.8 bar, with the middle layer being 2.06 mm thick while the other layers are 1.02 mm thick. 23. System according to one of Claims 13 to 22, characterized in that that the part is a reversing lever or angle lever. 909825/0633